Engine lock up

Lenny51

Lenny51

Member
My 8ba just rebuilt is on the test stand now it started for may be I minute & stoped the battery was very weak from spinning it over to get oil pressure up we charged the battery about it gave half a spin the nothing
thought the starter was hung up took the starter out thied to turn the flywheel with a 3 foot bar wont go eather way any ideas going to start tomorrow by taking the oil pan off yes there is 5 quarts of oil in it

I wached the guy put every together every thing turned freely new pistons & rings
new valves & springs new Isky cam new adjustable lifters all new bearings
new timing gears bored 60 over crank cut 10 under balanced offy heads
block magnfluxed
 
You could find if it is top end or bottom by pulling the front cover and taking the cam gear off.
 
What the guys found out some of the connecting rod bearings & crank journals are
scored up possible some dirt in the oil holes . it was still locked up until they loosened
some of the rod caps near the back of the engine , the crank shaft is back at the machine shop they are going to try & polish 1000th out they say when they cut a
crank it is impossible to be any dirt in the oil holes . before the engine was put
together saw my guy clean out the holes & the brush came out black . Now the question is who is going to pay for the new bearings & machine shop work
 
look and see if the plugs at ther rod journals (sludge trap? were replaced ----crud collects in the passage, the Merc crank has large ones and most times are full except for small passage----if the plugs are old you can say most likely it wasn't cleaned---and remains from the crank grinding would collecttoo---just blowind the passage out won't clean it
 
My guess - is that they didn't have enough clearance on the bearings, they didn't have enough oil in them . . . they got Hot . . . and that is that.

By the way, you really can't 'polish a crankshaft' to take off .001 correctly -- a polisher is for just that - polishing, not for truing up journals of taking material off to reduce a journal size. There are not many crank grinders that have the accuracy, machine or talent to take off .0005 of material (to give you .001 more clearance) on a crank that has already been ran. The fact that somebody is talking about needing .001 more clearance - tells me they had it wrong the first time. I'd be very suspect about the whole deal at this point.
 
I agree. There is no good way to polish .001 and maintain a flat journal surface. The outer edges will be all washed out. Maybe it will work because Flatheads are very forgiving but not something I want to do.

If the clean-out plugs have not been removed, it should be done.
 
I'm guessing there are multiple problems. 1 , they probably didn't clean out the crank, 2, clearances were never checked and were too tight. Make them fix it and I hope you haven't already paid them.
 
If the shop that did the work didn't use the correct bearing clearance, lockup is usual. If modern clearances were used, or the bearing inserts didn't match the crank journals, that could account for it. We always turn the crank by hand once it is back in the block. The piston ring gaps are important. They must measure .008-.013, or they will seize when the engine gets hot. Last one I saw locked up had "hydro-locked" due to a warped head that let coolant into one cylinder.
 
supereal said:
They must measure .008-.013, or they will seize when the engine gets hot.
Click to expand...

The low end of that is a really tight ring gap. What I normally see on mild street engines is about .0035 to .004 per inch of bore. BUT - I always just follow the ring manufacturer's recommendations - depending on the application.
 
I put bearing caps on using plastigage to make sure everything is ok. If that was not done then there is your problem. I think it would take a bit of dirt in the crank much longer than that to wipe out a bearing and even then it would lead to a knock.
 
At one time you could buy aluminum pipe plugs fron Red's headers for the Merc crank, on the ford cranks I used steel set screws.
 
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